Neither. Here's how to calculate the average profit per trade:

Code:
var AverageProfit = 0;
int Count = 0;
for(open_trades)
  if(TradeIsOpen) {
    AverageProfit += TradeProfit;
    Count++;
  }
if(Count) 
  AverageProfit /= Count;


Untested, so try it at your own risk..